1. Higher Human Biology Unit 2 Physiology & Health KEY AREA 4: Ante- and Postnatal Screening

2. Higher Human Biology We are going to build on the knowledge and skills that you developed during N5 and will learn about the following Physiology & Health key areas : - Key Area 1 – Reproductive Organs Key Area 2 –Hormonal Control of Reproduction Key Area 3 – Biology of Controlling Fertility Key Area 4 – Ante- and Postnatal Screening Key Area 5 – Structure and Function of Arteries, Capillaries and Veins Key Area 6 – Structure and Function of the heart Key Area 7 – Pathology of Cardiovascular Disease (CVD) Key Area 8 – Blood Glucose Levels and Obesity

3. Physiology & Health Learning Intentions KEY AREA 4 – Ante- and Postnatal Screening a)Antenatal Screening b)Postnatal Screening

4. 4a) Antenatal (before birth) screening - Examples Antenatal (prenatal) screening identifies the risk of a disorder so that further tests and a prenatal diagnosis can be offered Examples of Antenatal Screening are:- Ultrasound imaging (Dating Scan and Anomaly Scan) Biochemical tests Diagnostic tests Use of Karyotype Amniocentesis Chorionic villus sampling Rhesus antibody testing

5. 4b) Antenatal (before birth) screening - Ultrasound Ultrasound Imaging When the ultrasound scanner is held against a pregnant women’s abdomen, it picks up high-frequency sounds that have bounced off the fetus. These are converted to an ultrasound image on a computer screen Dating Scan Ultrasound imaging is carried out at 8-14 weeks to produce a Dating Scan, which is used to determine the stage of the pregnancy and to calculate the date when the baby is due to be born. Dating scans are used with biochemical tests for marker chemicals. Anomaly Scan Ultrasound imaging is carried out at 18-20 weeks to produce an Anomaly Scan, which detects the presence of any serious physical abnormalities in the foetus e.g. Spina bifida

6. 4c) Antenatal (before birth) screening - Biochemical Biochemical Tests Biochemical tests monitor the physiological changes that occur during pregnancy e.g. the concentrations of human chorionic gonadotrophin (HCG) Other routine tests to check the health of the pregnant women include:- Renal Function Tests Liver Function Tests Thyroid Function Tests White Blood Cell Counts Red Blood Cell Counts Protein concentration Glucose concentration Urea concentration Calcium concentration Alpha-fetoprotein (AFP)

7. 4d) Antenatal (before birth) screening - Diagnostic Diagnostic Testing A screening test is one that is used to detect signs and symptoms associated with a certain condition or disorder. If the signs are found, the probability that the individual is suffering the condition can be assessed as a degree of risk A diagnostic test is a definitive test that produces results that can be used to establish without a doubt whether or not the foetus is suffering a specific condition or disorder. Diagnostic tests may be offered to a pregnant women if:- Screening tests have shown a potential problem There’s a family history of a genetic disorder She belongs to a high-risk group (e.g. women over age of 35)

8. 4e) Antenatal (before birth) screening - Diagnostic A human karyotype shows the number and appearance of chromosomes found in a cell Amniocentesis and Chorionic Villus Sampling can be used to prepare a person’s karyotype which shows their complete chromosome complement Amniocentesis is carried out between 14-16weeks, and involves withdrawing amniotic fluid containing foetal cells. The cells are cultured, stained and examined under a microscope to create the karyotype and allows for chromosome abnormalities to be detected e.g. an extra chromosome 21 indicates Down’s Syndrome Disadvantage – risk of miscarriage Chorionic villus sampling (CVS) involves taking a tiny sample of placental cells using a fine tube inserted into the mothers reproductive tract. The cells are cultured and used for karyotyping. Benefit of CVS - it can be carried out at 8weeks whereas amniocentesis is 14-16weeks Disadvantage of CVS – causes a higher incidence of miscarriage than amniocentesis

9. 4e) Antenatal (before birth) screening - Diagnostic Blood Type Pregnant women have to have blood tests to determine their blood type. If a Rhesus- negative women is pregnant with a Rhesus-positive fetus, a potential problem arises:- Rhesus antigens on the fetus’s red blood cells are seen as foreign by the mother’s immune system, so if contact was made during birth there would be immune system problems To prevent problems, the mother is given Anti- Rhesus antibodies to destroy any Rhesus antigens left behind by the baby before her immune system has time to respond

10. 4f) Postnatal (after birth) Screening Diagnostic testing for metabolic disorders occurs when the baby is just a few days old In UK, ALL newborn babies are screened for PKU (Phenylketonuria) by having their blood tested for the presence of excess phenylalanine. PKU sufferers are then put on a restricted diet to prevent mental deficiency

11. Pedigree charts can be used to analyse patterns of inheritance in genetic screening and counselling Once phenotypes of family members are known, the genotypes can be worked out The construction of a family tree looking at genetic conditions/disorders is carried out by a genetic counsellor, in particular when a couple are concerned about passing the trait to their children X and Y chromosomes are called Sex Chromosomes and all other chromosomes are called Autosomes 4g) Genetic Screening and Counselling

12. 4h) Autosomal recessive inheritance A geneticist can spot the following patterns in autosomal recessive inheritance:- The trait is expressed relatively rarely The trait may skip generations The trait is expressed in some of the offspring of a consanguineous marriage (cousins) Males and females are affected in approximately equal numbers Genotypes of sufferers are homozygous recessive (ff) Genotypes of non-sufferers are homozygous dominant (FF), or heterozygous (Ff) EXAMPLE: Cystic Fibrosis

13. 4h) Autosomal recessive inheritance

15. 4i) Autosomal dominant inheritance A geneticist can spot the following patterns in autosomal dominant inheritance:- The trait is expressed in every generation Each sufferer of the trait has an affected parent When a branch of the tree fails to express the trait, the trait fails to reappear in future generations of that branch Males and females are affected in approximately equal numbers Genotypes of non-sufferers are homozygous recessive (hh) Sufferers are homozygous dominant(HH) or heterozygous (Hh) EXAMPLE: Huntington’s disease

16. 4i) Autosomal dominant inheritance

17. 4j) Autosomal incomplete dominance A geneticist can spot the following patterns in autosomal incomplete inheritance:- The fully expressed form occurs relatively rarely The partly expressed form occurs much more frequently Each sufferer of the fully expressed form has two parents who suffer from the partly expressed form Males and females are affected in approximately equal numbers All non-sufferers are homozygous for one incompletely dominant allele (HH) All sufferers of the fully expressed form are homozygous for the other incompletely dominant allele (SS) All sufferers of the partly expressed form are heterozygous for the two alleles (HS) EXAMPLE: Sickle-cell disease

18. 4j) Autosomal incomplete dominance

19. 4k) Sex-linked recessive traits A geneticist can spot the following patterns in sex-linked recessive inheritance:- Many more males are affected than females (if any) None of the sons of an affected male show the trait Some grandsons of an affected male show the trait All sufferers of the trait are homozygous recessive (male X h Y and very rarely the female X h X h ) Non-sufferers are homozygous dominant (X H Y or X H X H ) or heterozygous carrier females (X H X h ) EXAMPLE: Haemophilia

20. 4k) Sex-linked recessive traits

21. Physiology & Health Questions KEY AREA 4 – Antenatal and Postnatal Screening 1.Testing Your Knowledge 1Page 146 Q’s 1-4 2. Testing Your Knowledge 2Page 155Q’s 1-3 3.What You Should KnowPage 156Q’s 1-18 4.Quick Quiz